The present invention is directed to an apparatus for applying stimulations to a patient comprising an optical stimulation signal generator producing stimulation signals which are supplied to the patient's eye.
The measurement of biomagnetic signals is constantly gaining significance for medical diagnostics, as disclosed by the periodical "Bild der Wissenschaft", No. 8, 1986, pages 76-83. The extremely weak biomagnetic signals can be metrologically acquired with the assistance of a SQUID (superconducting quantum interference device) system, for example a system which can acquire the evoked magnetic fields of the human brain that lie on the order of magnitude of only 10.sup.-14 T. The subject is thereby brought into a magnetically shielded measuring space and his head is sensed in a non-contacting fashion with the SQUID system. The data acquired with the assistance of the SQUID technology are then interpreted with the assistance of a computer, based on certain mathematical models.
Magnetic fields induced in the brain by auditory or visual stimuli are of particular interest for experimental research and diagnostics. An apparatus used for the stimulation with optical stimuli must meet certain demands.
It must be taken into consideration that the measurement of optically evoked potentials or magnetic fields at the patient is carried out in a special environment. This can thereby, particularly, involve an electrical or magnetic shielding chamber, the magnetic field of a MR magnet or the proximity of diagnosis and/or therapy equipment, including monitoring and surgical equipment and apparatus working with gas.
It must then be taken into consideration that the measurement is to be carried out with optimally few disturbing influences. Thus, optimally few disturbances should act on the measuring apparatus of the electrical potentials or magnetic fields, for example a SQUID system, on the apparatus for stimulation itself or on the diagnostics equipment, for example an MR recording unit, and on the therapy equipment and, finally, on the subject as well. Relaxation and concentration of the subject are precisely what is necessary for a good signal quality.
Insofar as possible, finally, the measurement should also be capable of being carried out with an optimally great variety of scope or scope of variations in the stimulation in order to also be able to test higher brain functions of the subject.
Optical evokation has heretofore been primarily carried out based on two principles. The first principle is that the subject was shown a checkerboard pattern, for example a field of light and dark portions that are generated with an apparatus similar to a slide projector, with a specifically driven television monitor, or by means of a LED matrix. This checkerboard pattern was directly observed by the subject. Disturbing influences could not be suppressed due to the proximity of the equipment generating the checkerboard pattern.
The second principle is that the eye of the subject was exposed to light flashes that were produced with a flash bulb. This involved a rough function test of the optical signal processing in the brain. Collaboration on the part of the patient, particularly by focusing on a definite spot, was not necessary. Given this principle, eyeglasses could also be used, whereby the light flashes were generated directly in front of the eyes.
In another field, namely that of flight simulation for training pilots, it is known per se to integrate a projection surface into the pilot's helmet. The image presented to the pilot is generated by projectors behind the pilot and is transmitted through fiberglass lenses onto the screen in the helmet, as disclosed in an article from "Spektrum der Wissenschaft", September 1986, pages 56-64, particularly FIG. 3 on page 59.